The purpose of this proposal is to respond to RFA-HD-12-202 by continuing a multi-disciplinary research center on learning disabilities (LD), the Texas Center for Learning Disabilities. Consistent with the goals of RFA, we focus on definition and measurement issues, executive functions, interventions addressing reading comprehension, and the neurobiological correlates of LD. The central theme is that assessments of instructional response operationalize the historically prominent component of the LD construct, unexpected underachievement, which must be evaluated in children who respond inadequately to instruction, establish a reliable and valid classification of LD, inadequate responders should be systematically studied from instructional, neurobiological, and cognitive perspectives. To accomplish these goals, we propose to continue a multi-disciplinary center that includes four Projects and four Cores. Project 1 (Classification and Integration) continues to evaluate classification issues pertinent to LD through evaluation of actual data and simulated data, including the reliability and validity of classifications based on RTI. Project 1 also continues empirical syntheses involving the correlates of intervention response (including executive functions) and intervention outcomes. Project 2 (Executive Functions) provides a measurement study designed to address differences in models of executive functions from frameworks in neuropsychology, cognitive neuroscience, and education. It also introduces three design experiments on the role of executive functions in reading comprehension intervention. Project 3 (Intervention) follows up the previous 5 years of intervention research with 2 two-year randomized controlled trials of studies of Grade 4 students with identified reading comprehension problems. In Study 1, comparisons are made of Language/Knowledge or Skills/Strategies vs. Business as Usual (BAU). Study 2 compares a hybrid intervention in which the Study 1 interventions are integrated with and without executive functioning elements based in part on the design experiments in Project 2. Project 4 (Neuroimaging) will provide structural and functional neuroimaging studies of children who respond adequately and inadequately to Project 3 interventions, imaging executive function, word level, and sentence comprehension tasks. The Cores include the Administrative Services Core (A), the Service Core (B), the Data Management and Statistics Core (C), and the Assessment and Recruitment Core (D).